Showing papers by "Philips published in 1990"

Specifying real-time properties with metric temporal logic

Abstract: This paper is motivated by the need for a formal specification method for real-time systems. In these systemsquantitative temporal properties play a dominant role. We first characterize real-time systems by giving a classification of such quantitative temporal properties. Next, we extend the usual models for temporal logic by including a distance function to measure time and analyze what restrictions should be imposed on such a function. Then we introduce appropriate temporal operators to reason about such models by turning qualitative temporal operators into (quantitative) metric temporal operators and show how the usual quantitative temporal properties of real-time systems can be expressed in this metric temporal logic. After we illustrate the application of metric temporal logic to real-time systems by several examples, we end this paper with some conclusions.

A fast-settling CMOS op amp for SC circuits with 90-dB DC gain

Abstract: A technique that combines the high-frequency behavior of a single-stage op amp with the high DC gain of a multistage design is presented. This technique is based on the concept that a very high DC gain can be achieved in combination with any unity-gain frequency achievable by a (folded-) cascode design. Bode-plot measurements for an op amp realized in a 1.6- mu m process show a DC gain of 90 dB and a unity-gain frequency of 116 MHz (16-pF load). Settling measurements with a feedback factor of 1/3 show a fast single-pole settling behavior corresponding to a closed-loop bandwidth of 18 MHz (35-pF load) and a settling accuracy better than 0.03%. This technique does not cause any loss in output voltage swing. At a supply voltage of 5.0 V an output swing of about 4.2 V is achieved without loss in DC gain. The above advantages are achieved with a 30% increase in chip area and a 15% increase in power consumption. >

First-principles calculation of the magnetocrystalline anisotropy energy of iron, cobalt, and nickel

Abstract: The magnetocrystalline anisotropy energies of the elements iron, cobalt, and nickel have been calculated by means of the linear muffin-tin orbital (LMTO) method in the atomic-sphere approximation (ASA) within the framework of the local-spin-density approximation (LSDA). The so-called ``force theorem'' is used to express the total-energy difference, when spin-orbit coupling is included, as a difference in sums of Kohn-Sham single-particle eigenvalues. The results depend strongly on the location and dispersion of degenerate energy bands near the Fermi surface, and particular attention must be paid to the convergence of the Brillouin-zone integral of the single-particle eigenvalues. The calculated values of the anisotropy energy are too small by comparison with experiment, and we do not predict the correct easy axis for cobalt and nickel. We find that the variation of the anisotropy energy with changes in strain, in the magnitude of the spin-orbit coupling, for different choices of the exchange-correlation potential and for varying numbers of valence electrons are not capable of explaining these incorrect results. By comparing our calculated energy bands with those obtained by a full-potential linear augmented plane wave (FLAPW) method we conclude that the discrepancy is not attributable to terms in the potential that are neglected in the ASA.

The algebraic basis of mathematical morphology. I. dilations and erosions

Abstract: Mathematical morphology is a theory of image transformations and functionals deriving its tools from set theory and integral geometry. This paper deals with a general algebraic approach which both reveals the mathematical structure of morphological operations and unifies several examples into one framework. The main assumption is that the object space is a complete lattice and that the transformations of interest are invariant under a given abelian group of automorphisms on that lattice. It turns out that the basic operations called dilation and erosion are adjoints of each other in a very specific lattice sense and can be completely characterized if the automorphism group is assumed to be transitive on a sup-generating subset of the complete lattice. The abstract theory is illustrated by a large variety of examples and applications.

Links between Markov models and multilayer perceptrons

Abstract: The statistical use of a particular classic form of a connectionist system, the multilayer perceptron (MLP), is described in the context of the recognition of continuous speech. A discriminant hidden Markov model (HMM) is defined, and it is shown how a particular MLP with contextual and extra feedback input units can be considered as a general form of such a Markov model. A link between these discriminant HMMs, trained along the Viterbi algorithm, and any other approach based on least mean square minimization of an error function (LMSE) is established. It is shown theoretically and experimentally that the outputs of the MLP (when trained along the LMSE or the entropy criterion) approximate the probability distribution over output classes conditioned on the input, i.e. the maximum a posteriori probabilities. Results of a series of speech recognition experiments are reported. The possibility of embedding MLP into HMM is described. Relations with other recurrent networks are also explained. >

dc Electrical Degradation of Perovskite‐Type Titanates: III, A Model of the Mechanism

Abstract: A quantitative model for the dc voltage-induced resistance degradation is based on the defect structural material constants and a numerical solution of the general transport problem for the mixed-conducting perovskite-type titanates. During degradation, a demixing of the initially homogeneous oxygen vacancy concentration in nominally undoped and acceptor-doped systems occurs since the ionic transfer is (at least partially) blocked at the electrodes. Because of the specific defect structure, the concentration polarization of the oxygen vacancies leads to a pronounced increase of the p-conductivity in the anodic region and formation of an n-conducting cathodic region. The results of our phenomenological degradation studies concerning the influence of external parameters and material parameters as well as the time evolution of the field distribution and the electro-coloration are described by our simulation model with reasonable precision. The thermodynamic and kinetic aspects of the demixing process are discussed and compared to related phenomena.

Companding current-mode integrator: A new circuit principle for continuous-time monolithic filters

Abstract: A new companding current-mode (CI) integrator principle is proposed. The integrator function is linear despite being composed of nonlinear parts. Its application promises monolithic filters with improved noise performance suitable for low supply voltages. A class AB circuit implementation is proposed which features an extended dynamic range.

Embedded commericals within a television receiver using an integrated electronic billboard

Abstract: A television receiver is equipped with a graphics generator which is capable of generating a single or multiple graphic images from data representing commercial advertisements stored in a memory device. The elements of this arrangement include a micro-controller, a memory device, a graphics and memory controller, a pallet controller and a video switch. The images corresponding to the commercial advertisements are displayed to the consumer when a control function of the television receiver is activated. Alternatively, the images may be displayed in response to an internal clock. The images presented may be static or animated and may occupy a small portion of the screen or the full screen.

Metabolic imaging of patients with intracranial tumors: H-1 MR spectroscopic imaging and PET.

Abstract: Hydrogen-1 magnetic resonance (MR) spectroscopic images of patients with intracranial tumors were obtained. Metabolite maps of N-acetyl aspartate, choline, lactate, and creatine concentrations were reconstructed with a nominal spatial resolution of 7 mm and a section thickness of 25 mm. The metabolite maps showed variations in metabolite concentrations across the tumor. In one patient, it was observed that choline concentration was increased in one part of the tumor but decreased in another part. In another patient, the concentration of N-acetyl aspartate was extremely low in one part of the tumor but only slightly increased in another part of the tumor. Lactate was observed in all patients. In one patient, a combined measurement made with positron emission tomography (PET) and MR spectroscopic imaging was performed. This demonstrated that increased lactate concentration measured with H-1 MR spectroscopic imaging corresponded topographically with increased glucose uptake measured with fluorine-18 fluoro-2-deoxyglucose PET. Combined MR spectroscopic and PET measurements provide an opportunity to investigate, in greater detail than before, glucose uptake and catabolism by intracranial tumors.

Expression of a stilbene synthase gene in Nicotiana tabacum results in synthesis of the phytoalexin resveratrol.

Abstract: A gene from groundnut (Arachis hypogaea) coding for stilbene synthase was transferred together with a chimaeric kanamycin resistance gene. It was found to be rapidly expressed after induction with UV light and elicitor in tobacco cells (Nicotiana tabacum). Comparative studies of stilbene synthase mRNA synthesis in groundnut and transgenic tobacco suspension cultures revealed the same kinetics of gene expression. Stilbene synthase specific mRNA was detectable 30 minutes after elicitor induction and 10 minutes after UV irradiation. The maximum of mRNA accumulation was between 2 and 8 hours post induction. 24 hours after induction stilbene synthase mRNA accumulation ceased. Furthermore, in transgenic tobacco plants, the gene was found to be inducible in sterile roots, stems and leaves. Stilbene synthase was demonstrated in crude protein extracts from transgenic tobacco cell cultures using specific antibodies. Resveratrol, the product of stilbene synthase, was identified by HPLC and antisera raised against resveratrol.

Flow velocity profile via time-domain correlation: error analysis and computer simulation

Abstract: An ultrasonic human-blood-flow velocity profile measurement method using time-domain correlation of consecutive echo pairs has been developed. The time shift between a pair of range gated echoes is estimated by searching for the shift that results in the maximum correlation. The time shift indicates the distance a group of scatterers has moved, from which flow velocity is estimated. The basis for the computer simulations and error analyses of the scheme includes a band-passed white Gaussian noise signal model for an echo from a scattering medium, the estimate of flow velocity from both a single scatterer and multiple scatterers, and a derived precision estimation. The error analysis via computer simulation includes an evaluation of errors associated with the correlation method. For a uniform flow velocity profile, beamwidth modulation represents the greatest error source. However, for a nonuniform flow velocity profile, the jitter caused by a small flow velocity gradient can exceed the other error sources. A detailed computer simulation evaluated the interdependencies of window length, beam width, vessel diameter, and viewing angle on the estimation of flow velocity. >

A realistic fault model and test algorithms for static random access memories

Abstract: Testing static random access memories (SRAMs) for all possible failures is not feasible and one must restrict the class of faults to be considered. This restricted class is called a fault model. A fault model for SRAMs based on physical spot defects, which are modeled as local disturbances in the layout of the SRAM, is presented. Two linear test algorithms that cover 100% of the faults under the fault model are proposed. A general solution is given for testing word-oriented SRAMs. The practical validity of the fault model and the two test algorithms are verified by a large number of actual wafer tests and device failure analyses. >

Global Convergence of Genetic Algorithms: A Markov Chain Analysis

Abstract: In this paper we are trying to make a step towards a concise theory of genetic algorithms (GAs) and simulated annealing (SA). First, we set up an abstract stochastic algorithm for treating combinatorial optimization problems. This algorithm generalizes and unifies genetic algorithms and simulated annealing, such that any GA or SA algorithm at hand is an instance of our abstract algorithm. Secondly, we define the evolution belonging to the abstract algorithm as a Markov chain and find conditions implying that the evolution finds an optimum with probability 1. The results obtained can be applied when designing the components of a genetic algorithm.

A Petrov-Galerkin type method for solving Axk=b, where A is symmetric complex

Abstract: Discretization of steady-state eddy-current equations may lead to linear system Ax=b in which the complex matrix A is not Hermitian, but may be chosen symmetric. In the positive definite Hermitian case, an iterative algorithm for solving this system can be defined. The residual vectors can be made mutually orthogonal by means of a two-term recursion relation which leads to the well-known conjugate gradient (CG) method. The proposed method is illustrated by comparing it with other methods for some eddy current examples. >

Genetic Local Search Algorithms for the Travelling Salesman Problem

Abstract: We briefly review previous attempts to generate near-optimal solutions of the Traveling Salesman Problem by applying Genetic Algorithms. Following the lines of Johnson [1990] we discuss some possibilities for speeding up classical Local Search algorithms by casting them into a genetic frame. In an experimental study two such approaches, viz. Genetic Local Search with 2-Opt neighbourhoods and Lin-Kernighan neighbourhoods, respectively, are compared with the corresponding classical multi-start Local Search algorithms, as well as with Simulated Annealing and Threshold Accepting, using 2-Opt neighbourhoods. As to be expected a genetic organization of Local Search algorithms can considerably improve upon performance though the genetic components alone can hardly counterbalance a poor choice of the neighbourhoods.

Detection of metabolic heterogeneity of human intracranial tumors in vivo by 1H NMR spectroscopic imaging.

Abstract: Patients with intracranial tumors (gliomas) were examined by means of localized water-suppressed 1H NMR single volume spectroscopy and spectroscopic imaging. The 1H NMR spectra of the tumors exhibit signal intensities of the N-acetyl aspartate, choline compounds, and creatine plus phosphocreatine resonance lines that are different from the corresponding intensities observed on normal brain tissue. Also, for 6 out of the 10 patients examined so far, lactate resonance lines were detected in the tumor spectra. For one patient, abnormal 1H NMR spectra were obtained of a hemisphere which appeared normal with 1H NMR imaging. Metabolic heterogeneity of the tumorous regions could be demonstrated with 1H NMR spectroscopic imaging, using a spatial resolution in the order of 1 cm. These results suggest a spectrum of metabolic observations that may ultimately provide an important means for characterizing brain tumors.

Fine structure of excitons in type-II GaAs/AlAs quantum wells.

Abstract: Optically detected magnetic resonance in zero field as well as in a finite magnetic field has been used to study the excitons in type-II GaAs/AlAs quantum wells. The spectra are analyzed using the appropriate spin Hamiltonian for the quasi-two-dimensional indirect excitons. The electron-hole exchange interaction and the g factors for the electron and hole are obtained for several thicknesses of the GaAs and AlAs layers. Good agreement exists between the trend in the exchange interaction and the effective-mass theory of Rejaei Salmassi and Bauer. The anisotropy of the electron g factor is in accordance with a lifting of the threefold degeneracy of the AlAs X conduction-band minimum by the quantum-well potential giving the ${\mathit{X}}_{\mathit{z}}$ valley the lowest energy in the thin-layer quantum wells studied. The effective heavy-hole g value of \ensuremath{\sim}2.5 is much smaller than in the bulk and depends on the GaAs well thickness. This is probably a consequence of the valence-band mixing in quantum-well structures. Two classes of excitons are observed, each with a symmetry that is lower than the anticipated ${\mathit{D}}_{2\mathit{d}}$ point-group symmetry for excitons in quantum wells. The actual symmetry of the type-II excitons and the width of the exciton resonances are related to the microscopic structure of the GaAs/AlAs interface.

A unified mobility model for device simulation

Abstract: A physics-based analytical model is presented that unifies the descriptions of majority and minority carrier mobility and that includes screening of the impurities by charge carriers, electron-hole scattering, clustering of impurities, and the full temperature dependence of both majority and minority carrier mobility The electron and hole mobilities are given as analytical functions of local variables: ionized donor, ionized acceptor, electron and hole concentrations, and the temperature The excellent agreement between the proposed model and published experimental data on the carrier mobility in silicon reinforces the model predictions on less investigated aspects of the mobility, eg the temperature dependence of the minority carrier mobility, which is distinctly different from that of the majority carrier mobility >

Non-invasive oximeter arrangement

Abstract: A sensor includes a pair of resiliently loaded jaws for receiving a finger, the sensor including a pair of fiber optic light transmitting guides secured in fixed spaced relation to one of the jaws for sensing blood in the finger tip. A control unit includes a light generator for transmitting light modulated at first and second frequencies to one of the guides via a light guide transfer section. The finger pulse modulates the received transmitted light. The modulated light is sensed by the other guide and returned to a receiver in the control unit via the transfer section for separating and demodulating the different frequency signals. The control unit includes a calculating unit which has two branches for processing and then combining by dividing the processed demodulated signals for determining the oxygen content of the blood from the relative magnitudes of the pulse-dependent modulation factor of the wave reflected from the finger.

Method of generating a unique number for a smart card and its use for the cooperation of the card with a host system

Abstract: A smart card (1) which includes a random access memory RAM (10) and a read-only memory PROM (7) incorporating a production key (PK), a distributor key (MK), a bearer code (CP) and a serial number (NS) generates a unique number (NU) which is stored in the memory RAM (10) in the card after execution of the following steps of a program which is specific of the card: a - modulo-2 addition and storage in the RAM (10) of the result: PK⊕MK=KMP, b - the encryption of a unique input message ME, generated by the card, by means of a reversible algorithm (ALG, ALB -1 ) using the key KMP: NU=ALG.sub.KMP (ME).

A parallel object-oriented language with inheritance and subtyping

Abstract: This paper shows that inheritance and subtyping can be introduced advantageously into a parallel object-oriented language, POOL-I. These concepts are clearly distinguished, because they deal with different aspects of programming. In this way several problems traditionally adhering to inheritance can be solved. The language POOL-I is a parallel object-oriented language with a strong typing scheme which includes genericity and dynamic binding. A novel and particularly powerful mechanism offers the possibility to manipulate and analyse types dynamically.

Positron-annihilation study of the half-metallic ferromagnet NiMnSb: Experiment.

Abstract: Spin-polarized measurements of the two-dimensional angular correlation of annihilation radiation in NiMnSb are presented. By making use of the inherent partial polarization of the positron beam and the alignment of the magnetic domains with the aid of an external magnetic field, the sum and difference of the spin-dependent contributions to the angular correlation have been obtained for integration directions 〈100〉, 〈110〉, and 〈111〉. The results are compared with calculated distributions. A least-squares analysis of the data yields a value of (-8.4\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ for the three-photon difference effect in NiMnSb and establishes the half-metallic character of the band structure with an accuracy of ${\mathrm{\ensuremath{\sim}}}_{\mathrm{\ensuremath{-}}0.02}^{+0.01}$ electrons per formula unit.

Transport through a finite one-dimensional crystal.

Abstract: We have studied the magnetotransport properties of an artificial one-dimensional crystal. The crystal consists of a sequence of fifteen quantum dots, defined in the two-dimensional electron gas of a GaAs/AlGaAs heterostructure by means of a split-gate technique. At a fixed magnetic field of 2 T, two types of oscillations with different amplitude and period are observed in the conductance as a function of gate voltage. A simple model demonstrates that the oscillations arise from the formation of a miniband structure in the periodic crystal, including energy gaps and minibands which contain fifteen discrete states.

Optical illumination system and projection apparatus comprising such a system

Abstract: An efficient illumination system for an image projection apparatus is described, which system comprises a radiation source (20), a concave reflector (21) and a first and a second lens plate (25, 28) each being provided with a matrix of lenses (26, 29) for forming superimposed images of the radiation source on the object (1) to be illuminated, the aspect ratio of the lenses (26, 29) corresponding to that of the object (1).

Designing an Object-Oriented Programming Language with Behavioural Subtyping

Abstract: This paper describes the design of the parallel object-oriented programming language POOL-I. We concentrate on the type system of the language and specifically on the aspects of subtyping and genericity. POOL-I is the first language we know of that includes subtyping and inheritance as completely separate language mechanisms. By decoupling these two, which have been strongly tied together in other statically typed object-oriented languages with inheritance, a much cleaner language design can be obtained and a much more flexible use of both mechanisms can be made in actual programs.

Mobile radio transmission system using preferred home service area

Abstract: A private mobile radio transmission system comprising a plurality of geographically spaced base stations (BS) defining a plurality of overlapping service areas (SA). The base stations are coupled for example by land-line communication links (CL) to a system controller (SC). Mobile stations (MS) equipped with simplex two-way radios are free to roam through the service areas. In order to be able to make a call with or via a base station it is necessary for the mobile station to be registered with the base station concerned. Details of the registration are stored by the mobile station concerned and the base station. In order to optimise on the usage of radio channels, details of a home base station are preprogrammed into each mobile station and when the mobile station wishes to register with a base station, it is instructed to try to register firstly with its own base station, on the basis that the majority of calls will be to and from the home service area and will require only one pair of frequencies, secondly with a base station of any other service area in its region, and thirdly with a base station of a service area in any other region. When registered with a service area other than its home one, the mobile station checks regularly to see if it is possible to register with its home service area.